This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: African-American men have the highest incidence of prostate cancer in the world. The incidence of prostate cancer in African-American men is 59% greater than in Caucasian men. The exact cause for the increased incidence of prostate cancer in African-American is unknown. However, a diet high in fat and/or a sedentary lifestyle may predispose African-African men to prostate cancer by affecting levels of serum factors that potentate the growth of the cancer cells such as free testosterone, sex hormone-binding globulin &#40;SHBG&#41;, insulin, insulin-like growth factor-1 &#40;IGF1&#41;, prostate-specific antigen &#40;PSA&#41;, and insulin-like growth factor binding proteins- 2 and 3. Aims and Objectives: 1. To recruit 40 African-American men between the ages of 40 and 70 who are at increased risk for developing prostate cancer and randomize them into an exercise intervention or control group. 2. To examine the effect of 12 days of aerobic exercise over 4 weeks on PSA levels in African-American men who have PSA levels under 4.0 ng/ml. 3. To examine the effect of 12 days of aerobic exercise on free and total testosterone, insulin, IGF1, and SHBG levels in African-American men. Progress to date: Data collection still in progress. Continuation of grant has been requested.